1. Field of the Invention
The present invention relates to heavy equipment, and more particularly to heavy lifting equipment that is used in commercial applications for lifting very heavy multi-ton objects that can weigh as much as several thousand tons. Even more particularly, the present invention relates to an improved heavy lifting apparatus that includes a pair of spaced apart trusses, each formed of a pair of booms, each pair being pinned at an upper boom end portion and load transfer carriages provided at the lower ends of the pair of booms, the carriages being connected with a tensile element (e.g., winch cable) that can be wound upon sheaves to increase the mechanical advantage. One of the carriages has a winch that pulls the cable and the two carriages together increasing the angle of inclination of each boom during a lift, a horizontal lifting beam being suspended below the booms for rigging the package to the horizontal beam.
2. General Background of the Invention
In the construction industry and at industrial plants, there is great expense associated with the lifting of very large objects such as chemical process vessels, large pieces of equipment, pre-fabricated buildings and the like. Such objects are typically lifted with one or more very large and expensive devices such as high capacity lifting booms or cranes.
These cranes must be brought into the facility and assembled on site before use when very large lifts are contemplated. This is a very time consuming and expensive operation costing millions of dollars, even for one lift in some cases where the load is very large (e.g., several thousand tons). Scheduling of large equipment can be critical, due to the limited number of very large capacity cranes world-wide and the time restraints and deadlines associated with plant expansions, turnarounds and renovations.
Some of the problems with the lifting of very large objects is the mobilization cost, the complex rigging that must be accomplished timely, and demobilization once the lift is completed.
Huge counterweights are required to equally distribute load, especially if soil conditions are less than perfect. With a crane, ground pressures can be 1000–5000 pounds per square foot. A foundation failure is one of the greatest concerns in any land heavy lift in the Gulf Coast area of the United States. With the present invention, soil bearing pressures are distributed to four carriages. Each carriage then further distributes the load in a balanced manner so that soil bearing pressure might be 100–500 pounds per square foot.
When moving the load (once lifted) over the ground, the present invention is far more stable than a crane that is walking a load. Another problem with crane lifts is that of a rotation or shifting of the object being lifted so that it hits the crane. During a lift, a crane boom is under such stress, that catastrophic failure can result when the object being lifted even lightly hits the crane.
The present invention can be positioned inside buildings without structural modifications that are required when an overhead crane is installed. The only constraint with the present invention is that the apparatus fit inside the building once assembled.
Cranes can also fail if the object being lifted moves (e.g., with wind load) out away from the center of the hook.